Gas combustion turbines are used for a variety of application such as driving an electric generator in a power generating plant or propelling a ship or an aircraft Firing temperatures in modern gas turbine engines continue to increase in response to the demand for higher efficiency engines Superalloy materials have been developed to withstand the corrosive high temperature environment that exists within a gas turbine engine However, even superalloy materials are not able to withstand extended exposure to the hot combustion gas of a current generation gas turbine engine without some form of cooling and/or thermal insulation.
Thermal barrier coatings are widely used for protecting various hot gas path components of a gas turbine engine The reliability of such coating is critical to the overall reliability of the machine The design limits of such coatings are primarily determined by laboratory data However, validation of thermal barrier coating behavior is essential for a better understanding of the coating limitations Such real world operating environment data is very difficult to obtain, particularly for components that move during the operation of the engine, such as the rotating blades of the turbine.
Despite the extreme sophistication of modern turbine engines, such as gas turbines for generating electrical power or aircraft engines for commercial and military use, designers and operators have very little information regarding the internal status of the turbine engine components during operation This is due to the harsh operating conditions, which have prevented the use of traditional sensors for collecting reliable information of critical engine components
There is an increasing demand for real-time structural health monitoring and prognostics of critical components in current turbine engines to meet the demanding requirements of the future Wireless telemetry systems including power supplies, sensors and transmitters are known, however, the harsh turbine environments encountered in the turbine engines along with the lack of long-term demonstrated sensor functionality, together with incapable signal transmission from hot sections render it difficult to meet the desired objectives Efforts have been carried out to demonstrate wireless telemetry capabilities for strain and temperature sensing, however, it is limited by the capability of the wireless transmitting package for gas turbine operating temperatures in excess of 500° C.
MEMS devices or sensors have been used or at least attempts have been made to MEMS devices in connection with systems for monitoring operating parameters of turbine components Such devices are integrated circuits that are fabricated and then mounted to a component substrate, however, the wireless telemetry packages have limited capabilities in gas turbine relevant conditions
Surface acoustic wave (SAW) devices are passive devices that sense a property in their region, i e temperature, strain, pressure, vibration, etc The device is interrogated by an antennae located a distance away, and when interrogated, the SAW device uses the interrogation pulse, powers up, and transmits its data SAW devices are typically fabricated from processes such as photolithography, ink jet printing, photoresist removal, and densification via thermal or laser methods Processes that include sintering and/or densification result in shrinkage and increasing material strain and limit the types of materials that can be processed to full density, without undergoing structural damage The materials that can be processed using such techniques limit the operation of the devices to about 600° C. In addition, the SAW devices must be attached to the component surface The attachment techniques used also limit operation of conventional high temperature SAW devices to less than 600° C.
Other methods for depositing high temperature capable materials as SAW devices might be used, such as chemical vapor deposition (CVD) and physical vapor deposition (PVD) techniques, such as pulsed laser deposition. However, these processes are limited in the compositions of materials they may produce, are very expensive to perform, and are limited in the size of component on which they may deposit devices
High temperature SAW devices have been demonstrated by few companies using metal or metal based composite systems, however, their performance has been demonstrated at temperatures up to about 650° C. for only a few hundred hours
Previously issued patents U.S. Pat. Nos. 8,033,072, 8,132,467, and 8,151,623 disclose thermocouple, strain gauge and wear sensors and connectors for use in temperatures exceeding 1200° C. that can be fabricated using thermal spray and masking technologies. However, the inventors of the subject invention are not aware of thermal spray and masking technologies being used to form thin film devices that are operable in temperatures exceeding 650° C. and up to about 1500° C.